EPJ Web of Conf.
Volume 284, 202315th International Conference on Nuclear Data for Science and Technology (ND2022)
|Number of page(s)||5|
|Section||Nuclear Data for Reactors|
|Published online||26 May 2023|
Measurement of the delayed-neutron yield in the thermal neutron induced fission of 239Pu
1 CEA Cadarache, DES/IRESNE/DER/SPRC/LEPh, 13108 Saint Paul Lez Durance Cedex, France
2 CEA Cadarache, DES/IRESNE/DER/SPESI/LP2E, 13108 Saint Paul Lez Durance Cedex, France
3 CEA Cadarache, DES/IRESNE/DTN/SMTA/LMN, 13108 Saint Paul Lez Durance Cedex, France
4 CEA Saclay, DRF/IRFU/DPhN/LEARN, 13108 Saint Paul Lez Durance Cedex, France
5 Institut Laue-Langevin, F-38042 Grenoble, France.
* Corresponding author: email@example.com
Published online: 26 May 2023
This article presents an experimental effort to provide high-quality data to improve the evaluation of the 239Pu delayed neutron yield in the thermal energy range. The set-up is composed of a long counter with sixteen 3He tubes, a fast shutter system to produce irradiation cycles with short rising/falling times, and a miniature fission chamber containing 114μg of 239Pu. The whole system was installed in the PF1B experimental zone of the Institut Laue-Langevin, which provides a cold neutron beam. The repetition of irradiation/decay cycles enables to saturate the delayed neutron precursors and to measure their yield through the observed activity, shortly after the beam-stop. The innovation of our measurement technique relies on the clear distinction between prompt and delayed neutron counting, thanks to boron absorbers, without the necessity to move the sample. In such a way, it is possible to normalize the counting of delayed neutron emission to the one of total neutron emission, based on the well-known value of the prompt neutron multiplicity. The present work provides a delayed neutron yield value of vd = 0.642(5)%. The latter is in 1σ agreement with the IAEA recommendation of 0.628(38)%, with a strongly reduced uncertainty thanks to our normalization technique.
© The Authors, published by EDP Sciences, 2023
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